This PDF file contains the front matter associated with SPIE Proceedings Volume 9941, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

Organic light-emitting diodes (OLEDs) play an important role in the new generation of flat-panel displays. Conventional OLEDs employing fluorescent materials together with triplet–triplet annihilation suffer from a relatively low internal quantum efficiency (IQE) of ~62.5%. On the other hand, the IQE of OLEDs employing phosphorescent or thermally activated delayed fluorescence (TADF) materials can reach ~100%. However, these materials exhibit very broad peaks with a full-width at half-maximum (FWHM) of 70–100 nm and cannot satisfy the color-purity requirements for displays. Therefore, the latest commercial OLED displays employ blue fluorescent materials with a relatively low IQE, and efficient blue emitters with a small FWHM are highly needed. In our manuscript, we present organic molecules that exhibit ultrapure blue fluorescence based on TADF. These molecules consist of three benzene rings connected by one boron and two nitrogen atoms, which establish a rigid polycyclic framework and significant localization of the highest occupied and lowest unoccupied molecular orbitals by a multiple resonance effect. An OLED device based on the new emitter exhibits ultrapure blue emission at 467 nm with an FWHM of 28 nm, Commission Internationale de l’Eclairage (CIE) coordinates of (0.12, 0.13), and an IQE of ~100%, which represent record-setting performance for blue OLED devices.

Here, we developed a series of pyrimidine-based TADF emitters, 2-functionalized-4,6-bis[4-(9,9-dimethyl-9,10- dihydroacridine)phenyl]pyrimidine called Ac–RPM. We introduced a phenylacridine moiety into the 4,6-position of pyrimidine core to induce a twisted structure leading to a high PLQY of ~80%, and a small singlet and triplet excited energy difference of <0.20 eV. The optimized device realized a power efficiency of 62 lm W⁻¹, a high EQE_max of 25%, light-blue emissions with the Commission Internationale de l’Eclairage chromaticity (CIE) coordinates of (0.19, 0.37) and a low turn-on voltage of <3.0 V. Further, we investigated the strucutre–property relationship to unlock the potential of pyrimidine-based emitter. Consequently, we developed a green emitter realizing a power efficiency of over 110 lm W⁻¹ while maintaining extremely low voltages of 2.2 V at 1 cd m⁻² and 3.0 V at 1000 cd m⁻² at CIE of (0.36, 0.58). Apparently, these performances exceed those of previous TADF devices and are comparable to those of their state-of-the-art phosphorescent devices.

We hereby report the results of our direct investigation into the excited-state dynamics of thermally activated delayed fluorescence (TADF) molecules in solution using pump-probe transient absorption spectroscopy (TAS). We found that the charge-transfer (CT) state commonly stated for TADF molecules encompasses two forms: localized and delocalized CT states. A highly efficient TADF molecule, 4CzIPN [Uoyama et al., Nature, 492, 234-238 (2012)], showed both the localized and delocalized CT states, while an inefficient TADF molecule, 2CzPN, exhibited only a localized CT state. By analyzing the time profile of triplet species observed in TAS, we propose that the reverse intersystem crossing (RISC) of 4CzIPN occurs via a mutual interaction in multiple energy levels of localized neutral and CT states, and delocalized CT states.

Discovering new OLED emitters requires many experiments to synthesize candidates and test performance in devices. Large scale computer simulation can greatly speed this search process but the problem remains challenging enough that brute force application of massive computing power is not enough to successfully identify novel structures. We report a successful High Throughput Virtual Screening study that leveraged a range of methods to optimize the search process. The generation of candidate structures was constrained to contain combinatorial explosion. Simulations were tuned to the specific problem and calibrated with experimental results. Experimentalists and theorists actively collaborated such that experimental feedback was regularly utilized to update and shape the computational search. Supervised machine learning methods prioritized candidate structures prior to quantum chemistry simulation to prevent wasting compute on likely poor performers. With this combination of techniques, each multiplying the strength of the search, this effort managed to navigate an area of molecular space and identify hundreds of promising OLED candidate structures. An experimentally validated selection of this set shows emitters with external quantum efficiencies as high as 22%.

This study investigates an organic light-emitting diode (OLED) utilizing energy transfer from an excited complex (exciplex) comprising donor and acceptor molecules to a phosphorescent dopant. An exciplex has a very small energy gap between the lowest singlet and triplet excited states (S₁ and T₁). Thus, both S₁ and T₁ energies of the exciplex can be directly transferred to the T₁ of the phosphorescent dopant by adjusting the emission energy of the exciplex to the absorption-edge energy of the dopant. Such an exciplex‒triplet energy transfer (ExTET) achieves high efficiency at low drive voltage because the electrical excitation energy of the exciplex approximates the T₁ energy of the dopant. Furthermore, the efficiency of the reverse intersystem crossing (RISC) of the exciplex does not affect the external quantum efficiency (EQE) of the ExTET OLED. The RISC of the exciplex is inhibited when the T₁ energy of either donor or acceptor molecules is close to or lower than that of the exciplex itself. Even in this case, however, the ExTET OLED maintains its high efficiency because the T₁ energy of each component of the exciplex or the T₁ energy of the exciplex itself can be transferred to the dopant. We also varied the emission colors of ExTET OLEDs from sky-blue to red by introducing various phosphorescent dopants. These devices achieved high EQEs (≈30%), low drive voltages (≈3 V), and extremely long lifetimes (e.g., 1 million hours for the orange OLED) at a luminance of 1,000 cd/m².

Chrysene, which has a wide band gap, was selected as an emission core to develop and study new materials that emit ultra-deep-blue light with high efficiency. Six compounds introducing various side groups were designed and synthesized: 6, 12-bis(30,50-diphenylphenyl)chrysene (TP-C-TP), 6-(30,50-diphenylphenyl)-12-(3,5-diphenylbiphenyl-400-yl)chrysene (TP-C-TPB) and 6,12-bis(300,500-diphenylbiphenyl-40-yl)chrysene (TPB-C-TPB), which contained bulky aromatic si de groups; and N,N,N0 ,N0-tetraphenyl-chrysene-6,12-diamine (DPA-C-DPA), [12-(4-diphenylamino-phenyl)-chrysene-6-yl]-diphenylamine(DPA-C-TPA) and 6,12-bis[4-(diphenylamino)phenyl]chrysene (TPA-C-TPA), which contained aromatic amine groups, were designed to afford improved hole injection properties. The synthesized materials showed maxi mum absorption wavelengths at 342–402 nm in the film state and exhibited deep-blue photoluminescence (PL) emission s at 417–464 nm. The use of TP-C-TPB in a non-doped organic light emitting diode (OLED) device resulted in ultra-deep-blue emission with an external quantum efficiency (EQE) of 4.02% and Commission Internationale de L’Eclairage coo rdinates (CIE x, y) of (0.154, 0.042) through effective control of the internal conjugation length and suppression of the p –p* stacking. The use of TPA-C-TPA, which includes an aromatic amine side group, afforded an excellent EQE of 4.83 % and excellent color coordinates CIE x, y of (0.147, 0.077).

Controlling the energy level alignment at the ubiquitous interfaces in modern organic light emitting diodes, i.e., organic/electrode and organic/organic, is mandatory for achieving highest performance. While for some interfaces the understanding has matured over the past years – often with the help of photoelectron spectroscopy investigations, a lack of material-overarching and general models seems to persist. In this context, it is interesting to note that photoelectron experiments reported by different groups often returned a different level alignment for a given interface, which certainly should be unsettling for device engineers. It turns out that Fermi-level pinning and its consequences for charge density re-distribution across a device stack is an overarching mechanism that should always be considered. For intrinsic organic heterojunctions of materials with moderate acceptor/donor character the electrostatic potential across the interface changes only marginally – if at all. This situation, however, can be significantly altered when at least one of the two semiconductors is Fermi-level pinned by the "effective work function" of the other one, which is established by the contact to the electrode. Consequently, device engineering has to fully take into account the effect of adding the electrodes to a device stack, otherwise correlations between assumed electronic structure and device performance remain uncertain.

Many electron transport layer materials (ETL) employed in state of the art organic light emitting diodes (OLEDs) are known to be polar. We combine for the first time simulations and electrical characterization of OLEDs based on polar ETL, in order to understand the impact of such materials on the device operation. Depending on the orientation of the dipole orientation, simulations predict either a benefit or a disadvantage of the polar ETL for the device performance. We also show that OLEDs featuring a polar material are perfectly suited for extracting mobility activation energy and Injection barrier from the anode to the ETL.

We investigated a correlation between lifetime and the halogen element concentration in an organic light-emitting diode (OLED) and conducted experiments and simulations to discuss degradation mechanisms due to the halogen. OELD is generally formed of high-purity materials. Since the synthesis of high-purity materials takes time and cost, quantitative understanding of the kind, amount, and influence of impurities in OLED devices is expected. The results of combustion ion chromatography show that, if the chlorine concentration in the host material is more than several parts per million, the lifetime of the device is drastically reduced. The chlorine element, which is derived from the chlorinated by-product of the host material, is found to be transferred from the chloride to other materials (e.g., an emissive dopant) according to the results of LC-MS analysis. In addition, the electron transport layer including such impurities is also found to adversely affect the lifetime. The results of TOF-SIMS analysis suggest that the dissociated chlorine element diffuse to the light-emitting layer side when the device is driven. The results of simulations (Gaussian 09) and electrochemical analyses (cyclic voltammetry and electrolysis) reveal that the halogen element is easy to dissociate from halide by excitation or reduction. The halogen element can repeat reactions with the peripheral materials by excitation or reduction and cause damages, e.g., generate radicals or further reaction products due to the radicals. The results of simulation suggest that, such compounds have low energy level and become quenchers.

Conducting polymers, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been widely used as the hole injection layer (HIL) in many applications. However, in OLEDs the commonly used PEDOT:PSS has been found to have serious problems due to its inefficient holeinjection, inefficient electron-blocking, and substantial quenching of excitons close to the PEDOT:PSS. In the literature, tetrafluoroethylene-perfluoro-3,6-dioxa-4-methyl-7-octene-sulfonic acid copolymer, one of perfluorinated ionomers (PFI), was introduced into the PEDOT:PSS layer to develop a gradient work function (WF) by self-organization of the PFI. In this contribution, the self-organized gradient effect of this novel PEDOT:PSS:PFI layer were studied using multiscale analysis and dissipative particle dynamics (DPD) simulation. The DPD inter particle repulsion parameters and intramolecular bonding parameters were obtained by reverse mapping of a series of molecular dynamics simulations similar to that used in the earlier contributions. The calculated Flory-Huggins parameters indicated that the Nafion portion of the copolymer attracts PSS while the entire PFI molecule repulses PEDOT, which results in a PFI rich interface and a vertical gradient concentration distribution of PEDOT along the vertical direction of the film layer.

Design and development of highly efficient organic and organometallic dopants is one of the central challenges in the organic light-emitting diodes (OLEDs) technology. Recent advances in the computational materials science have made it possible to apply computer-aided evaluation and screening framework directly to the design space of organic lightemitting diodes (OLEDs). In this work, we will showcase two major components of the latest in silico framework for development of organometallic phosphorescent dopants – (1) rapid screening of dopants by machine-learned quantum mechanical models and (2) phosphorescence lifetime predictions with spin-orbit coupled calculations (SOC-TDDFT). The combined work of virtual screening and evaluation would significantly widen the design space for highly efficient phosphorescent dopants with unbiased measures to evaluate performance of the materials from first principles.

Organic light-emitting diode (OLED) devices are under widespread investigation to displace or complement inorganic optoelectronic devices for solid-state lighting and active displays. The materials in these devices are selected or designed according to their intrinsic and extrinsic electronic properties with concern for efficient charge injection and transport, and desired stability and light emission characteristics. The chemical design space for OLED materials is enormous and there is need for the development of computational approaches to help identify the most promising solutions for experimental development. In this work we will present examples of simulation approaches available to efficiently screen libraries of potential OLED materials; including first-principles prediction of key intrinsic properties, and classical simulation of amorphous morphology and stability. Also, an alternative to exhaustive computational screening is introduced based on a biomimetic evolutionary framework; evolving the molecular structure in the calculated OLED property design space.

Metal film is an essential part of the electrically pumped organic semiconductor lasers. But the large loss is the most important factor restricting the electrical pumping. In this paper, we investigate optically pumped amplified spontaneous emission (ASE) in the presence of metal films. The ASE threshold of device with metallic film is reduced by 2.5 times in comparison with that of the metal-free devices. The SiO₂ space layer with optimizing thickness between gain media and metal film can effectively prevent absorption loss but also provides a proper waveguide effect. Furthermore, the metal film can prevent the light leaking to the substrate and reflect the lights back into the media, which increases the intensity of pumping and emission again.

The development of Organic Light Emitting Diode (OLED), using an optically transparent substrate material and organic semiconductor materials, has been widely utilized by the electronic industry when producing new technological products. The OLED are the base Poly(3,4-ethylenedioxythiophene), PEDOT, Poly(p-phenylenevinylene), PPV, and Polyaniline, PANI, were deposited in Indium Tin Oxide, ITO, and characterized by UV-Visible Spectroscopy (UV-Vis), Optical Parameters (OP) and Scanning Electron Microscopy (SEM). In addition, the thin film obtained by the deposition of PANI, prepared in perchloric acid solution, was identified through PANI-X1. The result obtained by UV-Vis has demonstrated that the PET/ITO/PEDOT/PPV/PANI-X1/Al layer does not have displacement of absorption for wavelengths greaters after spin-coating and electrodeposition. Thus, the spectral irradiance of the OLED informed the irradiance of 100 W/m², and this result, compared with the standard Light Emitting Diode (LED), has indicated that the OLED has higher irradiance. After 1200 hours of electrical OLED tests, the appearance of nanoparticles visible for images by SEM, to the migration process of organic semiconductor materials, was present, then. Still, similar to the phenomenon of electromigration observed in connections and interconnections of microelectronic devices, the results have revealed a new mechanism of migration, which raises the passage of electric current in OLED.

Electrical doping is an important method in organic electronics to enhance device efficiency by controlling Fermi level, increasing conductivity, and reducing injection barrier from electrode. To understand the charge generation process of dopant in doped organic semiconductors, it is important to analyze the charge transfer complex (CTC) formation and dissociation into free charge carrier. In this paper, we correlate charge generation efficiency with the CTC formation and dissociation efficiency of n-dopant in organic semiconductors (OSs). The CTC formation efficiency of Rb2CO3 linearly decreases from 82.8% to 47.0% as the doping concentration increases from 2.5 mol% to 20 mol%. The CTC formation efficiency and its linear decrease with doping concentration are analytically correlated with the concentration-dependent size and number of dopant agglomerates by introducing the degree of reduced CTC formation. Lastly, the behavior of dissociation efficiency is discussed based on the picture of the statistical semiconductor theory and the frontier orbital hybridization model.

We have fabricated blue organic light-emitting devices (OLEDs) with higher color purity and stability by optimizing the structure of the Glass/ITO/NPB(50 nm)/ BCzVBi (30 nm)/ TPBi (x nm)/Alq3(20 nm)/LiF/Al. The results show that the introducing of hole blocking layer(HBL) TPBi greatly can improve not only the color purity but the color stability, which owe to its higher the Highest Occupied Molecular Orbital (HOMO) energy levels of 6.2 eV. We expect our work will be useful to optimizing the blue OLEDs structure to enhancing the color property.

Recently, many studies have been conducted to improve the electroluminescence (EL) performance of organic lightemitting diodes (OLEDs) by using appropriate organic or inorganic materials as charge generation layer (CGL) for their application such as full color displays, backlight units, and general lighting source. In a stacked tandem white organic light-emitting diodes (WOLEDs), a few emitting units are electrically interconnected by a CGL, which plays the role of generating charge carriers, and then facilitate the injection of it into adjacent emitting units. In the present study, twostacked WOLEDs were fabricated by using tungsten oxide (WO₃) as inorganic charge generation layer and 1,4,5,8,9,11- hexaazatriphenylene hexacarbonitrile (HAT-CN) as organic charge generation layer (P-CGL). Organic P-CGL materials were used due to their ease of use in OLED fabrication as compared to their inorganic counterparts. To obtain high efficiency, we demonstrate two-stacked tandem WOLEDs as follows: ITO/HIL/HTL/HTL′/B-EML/ETL/N-CGL/P-CGL (WO₃ or HAT-CN)/HTL″/YG-EML/ETL/LiF/Al. The tandem devices with blue- and yellow-green emitting layers were sensitive to the thickness of an adjacent layer, hole transporting layer for the YG emitting layer. The WOLEDs containing the WO₃ as charge generation layer reach a higher power efficiency of 19.1 lm/W and the current efficiency of 51.2 cd/A with the white color coordinate of (0.316, 0.318) than the power efficiency of 13.9 lm/W, and the current efficiency of 43.7 cd/A for organic CGL, HAT-CN at 10 mA/cm², respectively. This performance with inserting WO₃ as CGL exhibited the highest performance with excellent CIE color coordinates in the two-stacked tandem OLEDs.

The feasibility of applying a five-inch diagonal white organic light-emitting diode (WOLED) as a desk lamp was experimentally investigated by quantitatively comparing its two-dimensional (2D) optical intensity profile to that of a traditional 3M desk lamp equipped with optical diffuser. The 2D optical distribution patterns as the function of vertical distances to a surface of a five-inch diagonal WOLED were obtained by using rapid rotating measurement technique consisted of a sample holder on a rotational stage and a fixed photo detector with optical power meter. The 2D optical intensity profile on a surface can be rapidly established in a relatively small space by recording the reading from the fixed photo detector as rotating the sample holder. This rapid measurement technique is suitable for practical application in quality engineering without larger space. A WOLED is a compact and thin lighting source with planar device structure without additional optical components. Its optical intensity profile on a plane is expected to be different from traditional lighting sources. The optical distribution pattern of a desk lamp requires a relatively large area on a surface with relatively uniformed intensity distribution. The quantitative analysis of the similarity between WOLED and 3M desk lamp was conducted by comparing the optimal zones defined as the area within 75% of the maximum intensity in 2D optical distribution pattern. Our preliminary result showed that the optimal zone of a five-inch diagonal WOLED at 45cm vertical distance is highly similar to that of the 3M desk lamp with optical diffuser.

In this study, we demonstrate a blue OLED with the EQE of 34% and power efficiency of 79.6 lm W-1 using low refractive index electron transporting layer which are the highest efficiencies ever reported in blue OLEDs. In addition, we quantitatively calculated maximum achievable outcoupling efficiencies according to change of refractive indices, which can be used to estimate the achievable outcoupling efficiency of OLEDs without fabrication. The simulation indicates that EQE over 60% can be achievable in PhOLEDs if refractive indices of consisting organic materials’ are close to 1.5.

In this paper, we will discuss the characteristics of the flexible sandwich electrode. We fabricate the MoO₃/Ag grids/MoO₃ via thermal deposition method. We will measure the bending test and the optical and electric characteristics. The conclusion of the MoO₃/Ag grids/MoO₃ will compare with the MoO₃/Ag film/MoO₃ and ITO flexible electrodes. This sandwich electrode will increase the transmittance by less silver coverage but the MoO₃/Ag grids/MoO₃ have lower sheet resistance compared with MoO₃/Ag film/MoO₃. Therefore, we propose this new electrode structure is proper for application of OLEDs.

Organic p-i-n diodes enable the development of highly efficient organic devices such as organic light-emitting diodes. Understanding charge carrier trapping in these diodes is essential to comprehensively describe their electrical behaviors and increase their efficiency further. Here, a new bias stress protocol is developed to study charge trapping and the influence of trapping on molecular doping in organic p-i-n diodes. The results are discussed with the help of a novel analytical model, which is capable of quantifying the density of trapped charges and the doping efficiency from capacitance spectroscopy. We propose that this combined experimental/modeling approach is versatile and can lead to an advanced understanding of trapping in organic electronic devices.

In this study, the efficiency of organic light-emitting diodes (OLEDs) was enhanced by depositing a CeF₃ film as an ultra-thin buffer layer between the ITO and NPB hole transport layer, with the structure configuration ITO/CeF₃ (1 nm)/NPB (40 nm)/Alq₃ (60 nm)/LiF (1 nm)/Al (150 nm). The enhancement mechanism was systematically investigated via several approaches. The work function increased from 4.8 eV (standard ITO electrode) to 5.2 eV (1-nm-thick UV-ozone treated CeF₃ film deposited on the ITO electrode). The turn-on voltage decreased from 4.2 V to 4.0 V at 1 mA/cm², the luminance increased from 7588 cd/m² to 10820 cd/m², and the current efficiency increased from 3.2 cd/A to 3.5 cd/A when the 1-nm-thick UV-ozone treated CeF₃ film was inserted into the OLEDs.

OLEDs(Organic Light Emitting Diodes) has been applied to lighting and display fields. OLEDs has many advantages such as no viewing angle and fast reaction rate and so on. However, OLEDs still has low brightening issue in lighting field. This research fabricates a simple and fast production line, to produce light extraction film of the OLED. Microparticles in light extraction film were provided to enhance light luminance efficiency of the OLED up to 90%. A simple and fast production line was designed and fabricated by mechanical processing mode. It can produce 20 pieces light extraction films within 1hour.

We report a newly developed deep-blue phosphorescent iridium complex exhibiting a narrow emission spectrum. The use of this complex resulted in a deep-blue organic light-emitting diode (OLED) with an external quantum efficiency (EQE) exceeding 30%. Two iridium complexes with a 4H-1,2,4-triazole ligand which has an adamantyl group at the 4-position were synthesized, with the resulting effects of the adamantyl group on photoluminescence (PL) behavior investigated. [Ir(Adm1)₃] having a 1-adamantyl group did not exhibit any emissions at room temperature, whereas [Ir(Adm2)₃] having a 2-adamantyl group exhibited a blue emission with a peak wavelength of 459 nm and a high PL quantum yield of 0.94. Structural transformations between the ground state and excited state were estimated by molecular orbital calculations, which suggests that [Ir(Adm1)₃] undergoes a considerably more extensive change than [Ir(Adm2)₃]. It is therefore probable that [Ir(Adm1)₃] ultimately experiences thermal deactivation owing to structural relaxation. Furthermore, an OLED was fabricated using [Ir(Adm2)₃] as a dopant. The associated electroluminescence spectrum had an emission peak at 457 nm and a relatively small shoulder peak at 485 nm, which are consistent with the PL spectrum. A narrowed emission spectrum with a full width at half maximum of 58 nm was obtained, leading to a deep-blue emission with high color purity (CIE, x = 0.15, y = 0.22). This device ultimately exhibited an extremely high EQE of 32% at 2 mA/cm², which was likely attributable to an increase in outcoupling efficiency via molecular orientation.

In this study, direct and inverted OLEDs (iOLEDs) were fabricated by using the polymer Super Yellow (SY) as the emissive material. By adding a 5 nm-thick layer of polyethylenimine ethoxylated (PEIE) on top of ITO/ZnO (indium tin oxide/zinc oxide) in the iOLEDs, its cathode work function was reduced of 1 eV. A thin layer of 1,3,5-tris(Nphenylbenzimidazol- 2-yl)benzene (TPBi) was further added by wet-process in the iOLEDs, blocking the holes at the PEIE/SuperYellow interface, so that the iOLEDs could finally reach much higher luminance compared to the direct OLEDs, maximum 40 000 cd/m², with a constant maximum efficiency of 15 cd/A (13 cd/A maximum for the direct OLEDs). Temperature dependent transient electroluminescence measurements were conducted in order to compare charge carriers mobilities and disorder in direct OLEDs and iOLEDs. It was shown that the holes mobilities are higher for direct OLEDs (4 10^-6 cm^²/(V.s)) than iOLEDs (1.5 10^-6 cm^²/(V.s)) while the width of the distribution of energy states (DOS), σ, and the positional disorder parameter, Σ, are comparable for both structures.

The scientific community and some sectors of industry have been working with organic dyes for successful applications in OLED´s, OSC´s, however, most of the used dyes and pigments are synthetic. In this work is investigated the use of natural dyes for its application in organic light emitting diodes, some of the studied species are chili, blackberry, guayacan flower, cochinilla, tree tomato, capuli, etc. In this study the dyes are deposited by direct deposition and SOL-GEL process doped with the natural organic dye, both methods show good performance and lower fabrication costs for dye extraction, this represents a new alternative for the fabrication of OLED devices with low requirements in technology. Most representative results are presented for Dactylopius Coccus Costa (cochinilla) and raphanus sativus´ skin.

In this article, we demonstrated an exceptional palladium complex that exhibits both phosphorescence and delayed fluorescence for use as an efficient emitter in OLEDs. Devices employing PdN3N achieved external quantum efficiencies in excess of 22% and remarkable device operational lifetime to 90% initial luminance estimated at over 30,000 h at a practical luminance of 100 cd/m². Further tuning of the phosphorescent and delayed fluorescent emission should have a great impact in the development of efficient and stable emitters for deep blue or white OLEDs.

A new type of organic light-emitting diode (OLED) has emerged that shows enhanced operational stability and large internal quantum efficiency approaching 100%, which is based on exciplexes in donor-acceptor (D-A) blends having thermally activated delayed fluorescence (TADF) when doped with fluorescent emitters. We have investigated magnetoelectroluminescence (MEL) and magneto-conductivity in such TADF-based OLEDs, as well as magnetophotoluminescence (MPL) in thin films based on the OLEDs active layers, with various fluorescence emitters. We found that both MEL and MPL responses are thermally activated with substantially lower activation energy compared to that in the pristine undoped D-A exciplex host blend. In addition, both MPL and MEL steeply decrease with the emitters’ concentration. This indicates the existence of a loss mechanism, whereby the triplet charge-transfer state in the D-A exciplex host blend may directly decay to the lowest, non-emissive triplet state of the additive fluorescent emitter molecules.